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Document the (in)security features of CTM, especially ctm_rmail.

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This commit is contained in:
Kris Kennaway 2000-01-11 07:46:33 +00:00
parent fac8edac5e
commit 3aa5f62f03
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=55796
2 changed files with 51 additions and 24 deletions
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28
usr.sbin/ctm/ctm/ctm.1
View File

@ -222,7 +222,33 @@ Pathnames can be selected for CTM's consideration using the
option.
.El
.Pp
.Sh SECURITY
.Pp
CTM is an
.Bf Em
INSECURE PROTOCOL
.Ef
- there is no authentication performed that the
changes applied to the source code were sent by a
trusted party, and so care should be taken if the
CTM deltas are obtained via an unauthenticated
medium such as email.
It is a relatively simple matter for an attacker
to forge a CTM delta to replace or precede the
legitimate one and insert malicious code into your
source tree.
If the legitimate delta is somehow prevented from
arriving, this will go unnoticed until a later
delta attempts to touch the same file, at which
point the MD5 checksum will fail.
.Pp
A future version of
.Fx
may solve this problem by authenticating CTM
deltas using cryptographic signatures, but in the
mean time it is strongly recommended that you
obtain the CTM deltas via FTP, and not via email.
.Sh ENVIRONMENT
.Ev TMPDIR,
if set to a pathname, will cause ctm to use that pathname

47
usr.sbin/ctm/ctm_rmail/ctm_rmail.1
View File

@ -364,30 +364,31 @@ to execute
.Xr ctm
on the (non-FreeBSD) machine that this example was taken from.
.Sh SECURITY
If you automatically take your mail and pass it to a file tree patcher, you
might think you are handing the keys to your system to the crackers! Happily,
the window for mischief is quite small.
.Nm ctm_rmail
is careful to write only to the directories given to it (by not believing any
.Dq /
characters in the delta name), and the latest
.Xr ctm
disallows absolute pathnames and
.Dq \&\.\.
in files it manipulates, so the worst you
could lose are a few source tree files (recoverable from your deltas).
Since
.Xr ctm
requires that a
.Xr md5
checksum match before it touches a file, only fellow
source recipients would be able to generate a fake delta, and they're such
nice folk that they wouldn't even think of it! :-)
.Pp
Even this possibility could be removed by using cryptographic signatures.
A possible future enhancement would be to use
.Nm PGP
to provide a secure wrapper.
CTM is an
.Bf Em
INSECURE PROTOCOL
.Ef
- there is no authentication performed that the
changes applied to the source code were sent by a
trusted party, and so care should be taken if the
CTM deltas are obtained via an unauthenticated
medium such as email.
It is a relatively simple matter for an attacker
to forge a CTM delta to replace or precede the
legitimate one and insert malicious code into your
source tree.
If the legitimate delta is somehow prevented from
arriving, this will go unnoticed until a later
delta attempts to touch the same file, at which
point the MD5 checksum will fail.
.Pp
A future version of
.Fx
may solve this problem by authenticating CTM
deltas using cryptographic signatures, but in the
mean time it is strongly recommended that you
obtain the CTM deltas via FTP, and not via email.
.\" This next request is for sections 1, 6, 7 & 8 only
.Sh ENVIRONMENT
If deltas are to be applied then